In the medical field of cardiovascular surgery, if any lesion occurs to the valve inside the heart due to some reason(s) to cause hypofunction of the heart, and internal medicine fails, it is generally necessary for surgeons to employ a surgical implantation approach where the affected valve that have lost its original function will be replaced with a valve prosthesis. Such heart valve prosthesis for the implantation surgery is currently classified into two types: the mechanical heart valve prosthesis and the heart valve bioprosthesis. The present invention concerns heart valve bioprosthesis. Depending on whether a stent (support frame) is present inside the valve, the heart valve bioprosthesis is classified into stented valve (support frame) and stentless valve (no support frame).
A stentless valve (no support frame) is made purely of biological tissues or a combination of biological tissues and terylene fabric. The valve leaflet is made of bovine, equine or porcine pericardium. The covering and suture edge (ring) is made of bovine or equine pericardium and/or terylene fabric. The stentless valve has the following advantages: due to the absence of a stent, it has outstanding compliance with the heart after implantation; the various parts of the valve leaflet experience minimal stresses and relatively little damage, thus having a long service life. The stentless valve has the following disadvantages: also due to the absence of stent (no support frame), positioning the valve is quite difficult during an implantation operation, so that the surgeon needs to have a high skill level, and it is difficult for the surgeon to perform precise implantation. Thus, its use is limited.
A stented valve (support frame) is generally made of three materials: metals or plastics, biological tissues, and terylene fabric (also called polyester fiber or polyethylene terephthalate or PET, hereinafter as terylene for short). Currently, the stented bioprosthetic valves (support frame) accounts for 95% of the valve bioprosthesis. The stented valve has the following advantages: due to the presence of a stent (support frame), it is convenient to position during surgical implantation, facilitating precise implantation by the surgeon. However, existing stented valves are traditionally made of three materials: biological tissues for making the valve leaflet, metallic (alloy) or polymeric material for making the support frame, and terylene fabric for making the covering material and the suture edge (ring). Such type of valves has the following disadvantages: 1) the terylene fabric, after implantation into the heart and being exposed to blood, leads to relatively high possibility of thrombus or increased bacterial attachment; 2) the support frame, as a structure formed by combination of metallic wires and a base made of metallic plates, is high in hardness but poor in elasticity and compliance, and the valve leaflets fatigue easily; 3) the support frame, being a structure formed by combination of metallic wires and a metallic base, is structurally complicated and difficult to manufacture, weldings between the metallic wires will potentially break; and 4) the valve has a relatively large total height such that the aortic valve tends to block the blood flow at the opening of the coronary artery and the mitral valve tends to impede the movement of the original sub-valvular structures after implantation into the heart.
Terylene fabric is used for making the covering material and suture ring for both stented and stentless valves. This is because, on the one hand, terylene fabric has excellent chemical inertness, sterilization resistance, good mechanical properties, low water absorption and relatively good biocompatibility. Specifically, terylene fabric can be sterilized by traditional technologies, without changing its inherent properties, and has many advantages, such as high strength, good elasticity, good wear resistance, good fatigue resistance, and good dimensional stability, etc. Also, terylene fabric has relatively good chemical inertness, can induce tissue growth, reacts well to fibrosis, and has been proved safe during its more than 50 years history of implantation. On the other hand, as it has a use history of decades, those skilled in the art, will generally use terylene fabric when designing the covering material and suture ring.
In addition, for manufacturing any type of heart valve prosthesis, different components have to be sutured manually. The suturing points and the spacing between these points depend solely on the experience of the technical operators, and it is difficult to control suturing quality and provide training.
In view of the outmoded design concept of the traditional heart valve bioprosthesis, the present invention is designed and developed to overcome the many disadvantages in use and function as a result of the complicated structure.